Dosimeters measure an individual's or an object's exposure to something in the environment, particularly to a hazard inflicting cumulative impact over longer periods of time, or over a lifetime. Radiation dosimeters measure exposure to ionizing radiation, such as x-rays, gamma rays, neutrons, alpha particles, beta particles, and other charged particles (e.g. protons for radiotherapy). This ionizing radiation remains undetectable by the human senses and the damage the radiation causes to the body is cumulative, related to the total dose received. Therefore, workers who are exposed to radiation, such as radiographers, nuclear power plant workers, doctors using radiotherapy, and workers in laboratories are often required to wear dosimeters so that the employers can keep a record of their exposure to verify that it is below legally prescribed limits. Thermally Stimulated Luminescence (TSL) dosimeters are the most common type of wearable dosimeters for ionizing radiation. Hand held dosimeters are also available for radiation detection and these include ionization based systems (e.g. Geiger counters) and systems with solid state detectors (e.g. MOSFETs using silicon semiconductors).
TSL dosimeters (for example, LiF:Mg:Ti) are widely used for accurate measurements of the radiation dose upon exposure to ionizing radiation. The ionizing radiation leads to trapped electrons and holes. The dose information is read by heating the dosimeter at a controlled rate to high temperatures. The integrated emitted luminescence intensity and the glow curves can be used to determine the radiation dose and radiation type. This type of dosimeter typically requires an expensive reader and a sophisticated time dependent temperature profile, the dose information can only be read after the irradiation has occurred, and the readout process destroys all dose information.
OSL dosimeters have recently been developed and the main commercial OSL dosimeter is based on Al2O3:C. BeO is also being researched as an OSL dosimeter compound. Exposure to ionizing radiation leads to trapped electrons and holes. The OSL read-out process is via exposure to light, and the emitted light intensity provides the dose information. This type of dosimeter has the advantage that dose information can be read by optical means, and no heating is required.
In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art.
It is an object of the present invention to provide an improved radiation dosimeter detection system that is capable of recording different types of dose information and/or an improved method of real-time dose rate monitoring, or to at least provide the public with a useful choice.